New Delhi, Jan 17 : Better technology may not end the pollution crisis. Rather, it would allow one to monitor even finer particles which would become new health threats.

While currently particle effluents in air -- PM10 and PM2.5, or particles with diameter less than 10 and 2.5 micrometers -- are the cause of major health crisis, sharper effluents like PM1 may become the next enemy, say environmental and health experts.

"Finer the particles, more dangerous they are -- but there are no current thoughts on that. We don't have standards on PM1 because of the lack of evidence. It is supposed to be much more dangerous for health," Dr Gufran Beig, Project Director, System of Air Quality and Weather Forecasting And Research (SAFAR), told IANS. He said the focus may shift to the finer particles a few years from now.

To curb vehicular emissions, India expects implementation of the Bharat Standard-VI (Euro-VI equivalent) compliant cleaner transport fuels across the nation by April 2020 and in Delhi by April 2018.

"As each technology improves other problems will arise. BS-VI and beyond, the particles also get sharper," Sunita Narain, Director General, Centre for Science and Environment (CSE), told IANS on the sideline of a panel discussion held here by the European Union.

She, however, said that while "we have no doubt about the effect of PM2.5", there is no evidence against PM1 at present.

PM2.5, though, is deemed to be dangerous to human health. In September 2017, a study released by the Energy Policy Institute at The University of Chicago stated that long-term exposure to PM2.5 had direct effect on life-expectancy, with average life of an Indian dropping by four years. The study said that people in Delhi could live nine years longer if particle pollutant meet the standards.

According to Anumita Roychowdhury, who heads the air pollution and clean transportation programme at CSE, as both fuel and technology improve, the particle emissions become smaller as observed in Europe, where Euro-VI standard fuel is being used. For this, she added, new emission standards would have to be set.

Even as little is known about the effect of PM1, and the World Health Organisation safety standards are yet to emerge, it is being monitored in India as a potential future threat.

"We have been monitoring PM1 at one location each in Delhi and Ahmedabad, and across 10 locations in Mumbai. Their inclining and declining trends are helping us understand a lot," said Dr Beig. He said once the pollutant criteria for the fine particles is set, standards would come.